https://doi.org/10.1140/epjc/s10052-024-12839-x
Regular Article - Theoretical Physics
Multi-tracing the primordial Universe with future surveys
1
Department of Physics and Astronomy, University of the Western Cape, 7535, Cape Town, South Africa
2
Department of Physics, Stellenbosch University, 7602, Matieland, South Africa
3
Institute of Cosmology and Gravitation, University of Portsmouth, PO1 3FX, Portsmouth, UK
4
National Institute for Theoretical and Computational Sciences (NITheCS), 7535, Cape Town, South Africa
Received:
16
January
2024
Accepted:
21
April
2024
Published online:
14
May
2024
The fluctuations generated by Inflation are nearly Gaussian in the simplest models, but may be non-Gaussian in more complex models, potentially leading to signatures in the late Universe. In particular, local-type primordial non-Gaussianity induces scale-dependent bias in tracers of the matter distribution. This non-Gaussian imprint in the tracer power spectrum survives at late times on ultra-large scales where nonlinearity is negligible. In order to combat the problem of growing cosmic variance on these scales, we use a multi-tracer analysis that combines different tracers to maximise any primordial signal. Previous work has investigated the combination of a spectroscopic galaxy survey with a 21 cm intensity mapping survey in single-dish mode. We extend this work by considering instead the case where the 21 cm intensity mapping survey is optimised for interferometer mode. As examples, we use two multi-tracer pairs of surveys: one at high redshift () and one at very high redshift (
). The 21 cm surveys are idealised surveys based on HIRAX and PUMA. We implement foreground-avoidance filters and use detailed models of the interferometer thermal noise. The galaxy surveys are idealised surveys based on Euclid and MegaMapper. Via a simple Fisher forecast, we illustrate the potential of the multi-tracer. Our results show a
20–30% improvement in precision on local primordial non-Gaussianity from the multi-tracer. Furthermore, we investigate the effects on constraints of varying the parameter of non-Gaussian galaxy assembly bias and of varying the parameters of the intensity mapping foreground filters. We find that the non-Gaussian galaxy assembly bias parameter causes a greater change in the constraints on local primordial non-Gaussianity than the foreground filter parameters.
© The Author(s) 2024
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